Modulating means for cooler control



Sept. 18, 1945. J. E. CHAPMAN MODULATING MENS FOR COOLER CONTROL 2 sneetsv-sheet 1 Filed Sept. '7, 1942 INVEN TOR.

l ANIUIIIIIEILIMHI' ATTORNEY.

Sept. 18, 1945. 1 E; cHAPMAN MODULATING MEANS Fon coo-LER CONTROL Filed sept. 7, 1942 2 sheets-sheet 2 ATTORNEY.

Patented 18, 1945 Monm'rmo MEANS Foa cooLEa comm. v

James E. Chapman, Los Angeles, Calif., assigner to The Garrett Corporation, Airesearch Manni'actnring Company division, InglewoocLCalif., a corporation of California Application September '7, A1942, Serial No. 457,811 2 Claims. (Cl. 257-2) This invention relates in general to oil cooling systems -for internalcombustion engines. The

invention has one application in the ield of oil coolers for aircraft engines.

One type of oil cooler now generally employed for aircraft installation comprises a cellulartype of heat exchanger having inlet and outlet openings which are respectively connected in series with the oil circulating system, a means for regulating the cooling action of the heat exchanger, and some form of control for the regulating means which acts to provide a ilow of oil from the cooler to the aircraft engine within a temperature and viscosity range satisfactory for efficient operation and lubrication of the engine.

, The heat exchanger is an oil container, often in the shape of a cylindrical drum, through which oil passes from an oil inlet to an oil outlet in heat exchange relation with metal tubes within' the drum, through which atmospheric air 'is passed by the action of the aircraft "propeller, supercharger or compressor means; or in consequence of the motion of the aircraft through the atmosphere.

The heat exchanger may include a supplementary, oil container in the form of an oil jacket or mufl'` surrounding a core or cooler proper in which the air tubes are mounted, or in the form of a. separate compartment, within the cooling chamber, or both, through which oil as it comes from the` engine may be passed to warm the cooling element.

To maintain constant the .temperature of the oil leaving the cooler, the rate of transfer of heat units from the oil to the refrigerant air must be regulated to compensate for changing conditions of the oil and air streams. This regu lation is accomplished in one type of cooler by varying the rate of ow of `air through the core by use of movable shutters, flaps, or other air stream controlling means which may be adjusted in position with respect tothe direction of the ally arises from an excessively rapid drop in the temperature of the atmospheric air or a rapid increase of air iiow to which the thermostatic control cannot as rapidly respond. The formation of layers of waxed oil on the air tubes restricts the new of oil through the core chamber, and may increase the pressure at the oil inlet of the cooler suiiiciently to burst or otherwise damage the cooler drum. Also, since the layers oi' waxed oil, being of low heat conductivity, act as heat insulators between the liquid oil and the air, the' oil iiowing through the cooler in a restricted path at high speed leaves the cooler at an unduly high temperature. This hot oil is a disadvantage in the operation ofthe engine and by causing the thermostat to hold the shutters open prevents the decrease in the cooling action of the cooler which is necessary to melt the congealed oil.

Excessive pressure may also develop in the cooler core in the absence of waxing of oil on the air tubes i! the core is lled with cold viscous oil when a cold engine is started, or for other reasons. A r

One object of the invention isthe provision of a cooling system of the character described having a thermostatic control of the heat exchanger regulating means, in which the iluid pressure drop between the cooler inlet andY cooler outlet or other spaced points in the oil passage is utilized under control of a thermostatV to operate in either direction a reversible means to open or closev the'shutters or other air ow regulating 'means in a simple, eiective, and reliable manner.

It is an-object of the invention to provideva iiuid cooling system with combined temperature and pressure control of the kind above described 'in which the temperature and pressure controls flow of air for varyingthe ow rateof air through the core'tubes in combination with an actuating means for giving .the adjustment. f

The problem of cil temperature control corn-v plicated bythe fact that under certain conditions congealing or waxing of the oilwithinthe core on the external'surfaces'oi' the air tubes or other heat exchange wallstakes place due to an abnormally rapid transfer of heat units fromthe oil tothe air or. to anunduly prolonged period of transfer of heat units from oil to air at a moderately rapid rate. This condition usushuttersv the movement oi.'

are combined in a novel and eective manner, aording 'structural simplicity and reliability performance. l i

In pursuance of this general object. it is an object of the invention to provide. a fluid cooling system'with a combined temperature-pressure control in which. thethermostatic control isv disconnected from. or its Voperation modified with respect to, the shutter operating means by the fluid pressure contr-clin; correspondence with a pressure dropin excess of a predetermined value.

It is another object of the invention to provide a uid cooling system :having a combined temperature and pressure control in which athermostat for effecting, the temperature control is bodily movable by a uidpressure operated `device responsive to the pressure drop in the cooler in a manner to vary the control action voi! the thermostat on the shutter operating means. It is a further object to provide a uid cooling system of the character described in which the thermostat is bodily moved by the means responsive to the pressure drop in the cooler in a manner to entirely nullify the control action of the thermostat on the shutter operating means and substitute therefor a control which operates to close the shutters to decrease the cooling capacity of 'the cooler.

It is a further object of the invention to provide a device of the character described in which the thermostat is bodily movable by reason of its of the live element of a thermostat working.

against a coiled spring or similar means tending to move the switch arm in the opposite direction, the overriding pressure control being accomplished by mounting the thermostat on a mov- .able piston like plunger from which the live element of the thermostat extends toward the switch arm and which is resiliently held in -a normal position toward the switch arm against a diierential iluid pressure exerted on its two active faces which is a measure of the diierential lluid pressure between the inlet and outlet of the cooler.

Further objects and advantages of the Ainvention will bebrought out in the following part of the specification.

Referring to the drawings which are for illustrative purposes only,

Fig. 1 is an elevational view partly in section and partly schematic of an ail cooling apparatus for an aircraft engine embodying this invention.

Fig. 2 is ya sectional view taken along the line 2-2 of Fig. 1.

Fig. 3 is a sectional view taken along the line 3-3 of Fig. 1.

Fig. 4 shows a portion of Fig. 3 with the thermostat housing in a different position.

The cooling apparatus of an oil cooling system for an internal combustion engine is described herein to illustrate this invention. As to some of its features. however, the invention has other oil cooling devices generally, but is to be given the scope of the appended claims.

A heat exchanger II` of the oil cooling apparatus shown in Fig. l comprises an oil container or core I2 constituting the oil cooler proper and a muil I3 which has the form of a cylindrical shell surrounding the core I2. The upper ends of the mun I3 are spaced apart to receive a rigidly related fitting I5, one end of the mui being in communication with an inlet chamber I5 of the fitting I5 through which it receives oil from the oil delivery piping I4 and the other end of the muff I3 being in communication with a chamber I1 of the fitting I5, through which oil passesl as it leaves the muil?. Oil from the chamber I1 may enter the core I2, passing therethrough in he'at exchange relation with the air tubes (not shown), leaving the core through a chamber It formed in the fitting I5. Arrows A indicate the path oi' the oil from the oil delivery piping ld through' the mun to the chamber I1, and arrows B indicate the path of the oil after it leaves the muil from the chamber I1 through the core I2 to the chamber Il.

A iitting I3 suitably securedto `the fitting it serves as a housing for the control mechanism oi the means for varying the cooling capacity of the core I2. The walls of the ntting I3 define a high pressure chamber 20 having a port 20a registering with the chamber I1 and a lowpressure chamber 2| having a port 2|a registering with the chamber I3. Oil passing through the core I2 intol the chamber IB flows through the low pressure chamber 2| to an outlet pipe 23 by whichoil is returned to the engine, as indicated by arrows C.

A partition wall 22 between the high pressure chamber 20 and the low pressure chamber 2| is formed with a port 25 through which oil may iiow from the'chamber I1 to the high pressure chamber 20 to the low pressure chamber 2|, as indicated by arrows D, under control of the check valve device 24, the spring 24a of'which is adjusted to open the valve 24 when the pressure dii ferential between the high pressure chamber 2li and the low pressure chamber 2| reaches a predetermined value. 'I'his pressure differential registers the drop in pressure in the oil stream as it ows through the core I2 from the chamber II to the chamber I8, and the pressure differential value at which the spring 24a permits opening of the port 25 is less by an adequate margin than that at which will occur bursting or other damage to the core, but is substantially greater than that required for proper and normal circulation of oil through the core. Upon opening of the check valve device 24 oil ilows, after it leaves the muii I3 and enters the chamber Il, into the high pressure chamber 25 through the port 25 into the low pressure chamber 2 I, and thence to the cooled oil; return piping 23 by which the oil is conducted back to the engine, as indicated by arrows D.

. The rate of ow of the refrigerant air through the core I2 is regulated by shutters 23 which are moved between relatively open and relatively closed limit positions by a reversible means which is illustrated in the form of a reversible motor 2l and power transmitting devices 28.

Operation of the motor 21 is regulated by a control mechanism designated generally by the figure 3|, which, by reference to Figs. 2 and 3. is seen to be contained within a chamber 32 dened by the walls of a projection 33 of the housing I9.

within a portion of the low pressurechamber 2| and within a neck 34 between the main body of" the tting I3 and the projection 33 thereof. This control mechanism 3| combines in a novel manner temperature and -pressure responsive elements, and will now be described.

A cylinder 35 is threadedly seated in fixed position in the bore of the neck 34. 'I'he cylinder is closed at its leftward end by a cylinder head nut 35. A plunger 31, constituting a pressure responsive means and also constituting a positioning means .for the thermostat of the control mechanlsm 3|, is slidably mounted in the cylinder 35. This plunger 3T comprises an outer drum 38 and an inner drum v39, the outer drum 33 being provided at its leftward end with an inturned flange 40, which is welded or otherwise secured to the inner drum 39. Sliding movement of the plunger or thermostat housing 3l within the cylinder 35 is guided by engagement of the leftward drum 33 with the bore tace of the cylinder 35, by` engagement of the inner drum 39 with an inwardly extending annular iiange 4| formed on the cylinder 35 and by engagement of a drum head 52 at the leftward end of the inner drum 39 with the bore face of the cylinder 35. The drum head 52 is formed with circumierentially arranged ports 52a and the flange 4I is similarly formed with circumferentially arrangedrports 42. The outer drum 38 is closed at its rightward end and the inner drum 39 has an inwardly turned flange 50 at its rightward vend providing an aperture 5I. The thermostat housing 31 is normally held in an extreme leftward position, in which the flange engages the flange 4|, by a coiled spring 53 seated between the flange 4| and the drum head 52.

The space between the cylinder 36 and the drum head 52, the space between the cylinder 35 and the leftward end portion of the inner drum 39, and the space within the inner drum 39, constitutes a chamber designated as 84.` As best shown in Fig. 2, this chamber 64 is in communication with the high pressure chamber through a passage 61 formed in the housing I9, an annular groove 85 in the outer threaded wall of the cylinder 35, and radial passages 38 connecting the groove 65 with the chamber 54. ,l

The left end of the piston 31 is subjected to the Vpressure in the high pressure chamber 25, `while the right end of the piston 31 is subjected to the pressure in the low pressure chamber 2|. The piston 31 is moved to the right against the action of the spring 55 whenever the pressure differential of chambers 20 and 2| exceeds a predetermined value.

The thermostat means of the invention is arranged as follows. The wall of the inner drum 39 is inwardly thickened near its rightward end to provide a cylinder 44. A diaphragm 48 of suitable elastic material', such as neoprene, is held seated against the right end of the cylinder 44 by a retaining ring |49 which bears against the flange 50. The diaphragm 4 8has a leftward extending disc shaped plug 48a which is preferably an integral part of the diaphragm and extends into the cylinder 44. A thermally expansible liquid or semi-liquid material 43 occupies the space between the outer drum 38 and the inner drum 39 and the space within the inner drum 39 to the right of the diaphragm 48, these two spaces being 'communicatingly connectedby the aperture 5|.

A live element 45 of the thermostat comprises a stem 41 and a piston 45 which slidably reciprocates within the cylinder 44. The piston 45 is resiliently held against the plug 48a by a coiled spring 54 seated between a iiange 53 on the stem 41 and the drum head 52. Upon expansion of the thermal material 43, the -diaphragm 43 is distorted leftwardly and the diaphragm plug 48a is moved to the leit which in turn gives a leftward movement to the piston 45 and stem 41.

The leit end of th'e stem 41 passes through a packing ring 55 in the cylinder head 3B and projects a short distance beyond the cylinder head 35 to laterally abut a switch arm 51 which is oscillatively mounted on a pivot pin 58 carried by a bracket arm 59 secured to the cylinder 35.

The switch arm 51 is held in contact with the stem 41 by a coiled spring Btl compressed between the switch arm 51 and a cover plate 33a on the projecting portion 33 of the fitting i9. The outer end of the switch arm 51 carries a movable con-l tact 6| which passes over a series of stationary contacts 62 as the switch arm 51 moves to and fro under the action of the thermostat. The stationary contacts 62 are respectively connected to conductors I3 leading into a cable 30 which in turn leads to a motor control switch box 29.

The electrical connections of the movable contacts 6|, stationary contacts 32, and within the control box 29 are such that when the movable contact 6| engages any one of the stationary contacts 62 to the left of the center line of a bracket 68upon which the stationary contacts are mounted, the motor 21v is operated to move the shutters 2B to a relatively open position, with respect to a shutter position which is about mldway between an extreme open position and an extreme closed position, the degree of `opening from this midway position for each contact varying with the extent of arcuate spacing of the movable contact 8|- tc the left of the center line of the bracket 68. When the movable contact 8|' engages the extreme leftwardstationary contact 62, the motor 21'moves the shutters to their extreme open position. Engagement of the switch arm 51 with the rightward contacts 62 operates to close the shutters according to a similar pat-f tern. i t

From the above description, it is apparent that so.long as the spring 58 holds the thermostat housing 31 in its extreme leftward position with the shoulder flange 40 against the shoulder flange 4|, variationsI intemperatures of the oil leaving the core i2 and flowing through the low pressure chamberli in vwhich the thermostat housing is disposed, are reflected in movements of the stem 41, which movements bring about operation of the motor 21 to move the shutters to relatively open positions in correlation with temperatures above the normal temperature of the oil returning to the engine and to move the shutters to relatively closed positions in correlation with temperatures of sub-normal value.

When. due to restriction of the flow of oil through the core l2 either due to the formation of layers of congealed oil on the air tubes within the core or due to high viscosity of the oil flowing through the core at a low temperature which the thermostat has not corrected or is correcting too slowly, the pressure differential between the chamber i1, at the core inlet, and the chamber i8, at the core outlet, increases to a predetermined value above normal, the action of the spring 56 is overcome and the thermostat hous- `ing 31 is caused to move to the right by the difference in fluid pressure in the chamber 64 and in the low pressure chamber 2|. The thermostat housing may then occupy a position as shown in Fig. 4. As this pressure differential is established and as' it increases, the spring 56 is gradually compressed, the entire assembly including the stem 41 begins a rightward movement and the movable contact 6|, irrespective of its position with relation to the stationary contact 62, also begins a rightward movement. The effect is to modify the action of the thermostat 31 lowering the oil temperatures which correspond respectively to the several positions of the switch arm 51, and 'thereby lowering the oil temperature which corresponds to any given position of the shutters 26 for any given set of aircraft operative conditions. This change in correlation of the thermostat to shutter position slows down the cooling action of the cooler and accelerates the liquefaction of the congealed oil in the core if the rise in pressure differential is due to that cause. If the rise in pressure differential is due to high viscosity of cold oil in the core, warming of this cold oil is accelerated.

li the pressure diderential becomes so great as to withdraw the stem Si well within the cylinder head 36, the resultant eect is to entirely disconnect the thermostat from engagement with the switch arm, allowing the switch arm' under the iniluence of the spring t@ to move to its extreme rlghtward position where the circuit is made which will completely close the shutters 2t, reducing the rate oi' extraction oi heat units from the oil to a minimum. Remembering that .the temperature of the outgoing oil is sometimes excessive when layers of congealed oil torni on the air tubes in the core, it will be observed that this high temperature is nevertheless powerless to cause the stem il to operate the switch arm ill' to open the shutters, beca-ilse the simultaneous high pressure dierential set up by the obstruction of the core is holding the thermostat housing el and the stem il in a suciently retracted positlon that even at the high oil temperature, it will not be projected from the'cylinder head 3o into engagement with the switch arm il?.

From the foregoing description, it will be seen that my invention provides a thermostatic control for the shutter operating means which thermostatic control is in turn controlled or its action modified by` a pressure differential responsive means. In addition to the broad combination, my invention also resides in the particular piston and thermostat arrangement which l have devised.

i claim as my invention:

l. ln an oil cooling system for an internal combustion engine, the combination of: an oil cooler having an oil inlet through which oil may be received from the engine and an. oil outlet through which oil may be discharged for return to the engine; means for varying the cooling capacity of said cooler; electric motor means for operating said varying means; an electric controller for said electric motor means having a, movable switch arm for operating said motor means to 'increase the cooling capacity of said cooler when moved in: a nrst direction and to decrease the cooling capacity or said cooler when moved in a second and opposite direction; a cylinder having a fixed head at one end and connected to said cooler inletz' a hollow plunger in said cylinder having a portion projecting therefrom in heat exchange relation with oil returning from said cooler to the engine and movable in one direction away from said head by uid pressure in said cylinderryieldable means for moving said plunger in the other direction; a temperature responsive means in said plunger; a member movable by'said temperature means with respect to said plunger in said other direction, said member projecting through said head in fluid tight relau tion therewith to separably engage said switch arm to move it in said rst direction; and yieldable means for moving said movable member in said other direction.

2. In an oil cooling system for an internal combustion engine, the combination of: an ollcooler having an oil inlet and an oil outlet there being an opening between said inlet and said outlet; v

means for varying the cooling capacity of said cooler; delivery piping connecting the oil outlet of the engine with the oil inlet of the cooler; return piping connected to said outlet for carrying cooled oil away from said cooler; thermostat means for controlling the operation of said varying means, said thermostat means having a Vpart exposed to the temperature of the oil and a movable pair of relatively movable members connected so that relative disposition thereof is responsive to the temperature of the oil and so that the disposition thereof determines the action of said varying means; and a wall movably disposed across -said opening between said inlet and said outlet so as to be moved by the pressure drop between said inlet andsaid outlet, said wall preventing substantial now of oil through said opening from said inlet to said outlet, and said wall being secured to said thermostat so as to bodily move the same, whereby the thermostat will change the disposition of said members inde- 

